Answer: 25%
Step-by-step explanation:
first you would take 500/20
To find whether the volume would be doubled when the radius is,we can find the volume of the two balloons.
The formula of a sphere is:

Let's take 丌 as 3.14
The volume of the balloon with 4cm radius:

The volume of the balloon with 8cm radius:

As we can see,
267.94668 × 2 = 535.89 ≠2145.56
Thus,she wouldn't discover that the volume is twice as big when the radius is doubled.
Hope it helps!
Answer:
Step-by-step explanation:
let be x the price before the discount
original price= 28/(1-0.25)=28/0.75=37.33
original price=37.33